Chemical process



May 15, 1945. B. E. ROETHELI Erm. 2,376,191

CHEMICAL PROCESS Filed sept. 12, 1942 2 sheets-sheet 1 SEPAPATOR May 15,1945 B. E. ROETHELI E'rAL 2,376,191

CHEMICAL PROCESS Filed Sept. l2, 1942 2 Sheets-SheetI 2 QUNCHIIVG dHAMBE a /70 REAdTo7@-\ 29 700 Patented May 15, 1945 CHEMICAL PROCESS BrunoE.

Scharmann,

Roetheli, Cranford, and Walter G. Westfield, N. J., assignors, by

mesne assignments, to Jasco, Incorporated, a corporation of LouisianaApplication September 12, 1942, Serial No. 458,086

(Cl. 26o-680) 2 Claims.

a continuation-in- Serial No. 407,550,

The present application is Dart of our prior application, filed August20, 1941.

'I'he present invention relates to improvements in the art ofdehydrogenating hydrocarbons and, more particularly, it relates to thedehydrogenation of hydrocarbons such as butylene to form butadiene undercontrolled conditions of temperature and contact time to enable theattainment of a high degree of selectivity.

In our prior application, Serial No. 407,550, We have disclosed meansfor obtaining very short contact times which may be less than 1 secondin duration. We have no discovered that by operating at somewhat lowertemperatures, say around 1100* F., we may extend the contact timebetween catalyst and reactants, and at these lower temperatures weprefer to operate the process in the range of from not less than 1 tonot more than seconds contact time between the reactants and thecatalyst in the reaction zone.

Our present invention may be suitably illustrated in a preferredmodification by the accompanying drawings which are identical with thosefiled in our prior application, Serial No. 407,550, Iiled August 20,1941.

Thus, in Fig. I we have shown a complete fiow diagram which discloses inconnection with the specification, a preferred modification of ourinvention; and in Fig. II there is shown an enlarged view of ourimproved reactor. Throughout the views similar reference charactersrefer to similar parts.

Referring in detail tothe drawings, I represents a hopper in which thereaction takes place. The internal construction of our improved reactoris shown in detail in Fig. II and will be subsequently described indetail in discussing that figure of the drawings. Catalyst in the formof powder having a particle size of from 200-400 mesh is also dischargedinto the reactor from another hopper (I0) in a manner that will bepresently explained. The hopper I0 contains a dehydrogenation powderedcatalyst preferably in a heated and activated condition and is incommunication at its lower end with a standpipe I2 projecting downwardlyasshown. This pipe may be of any convenient dimension, such as 36 inchesin internal diameter, and a vertical length of 40-60 ft. Thesedimensions are purely illustrative and are governed by the quantity ofcatalyst to be fed to the hopper in any particular case. The lowerend'fo the pipe is provided with a control valve I4 which is adapted tocontrol the rate of flow by gravity of powder in pipe I2 into thehorizontal bend I6. Horizontal bend I6 is in communication with upwardlyextending standplpe I8 which projects, as shown, into hopper I. In otherwords, the feed of catalyst to the reactor l is through a down-flow pipeI2 and an up-iiow standpipe I8. This flow may be accomplished byregulating the densities in pipes I2 and I8 respectively, by selectingthe proper pipe dimensions, coupled with the introduction of fluidizinggas as follows. First, to cause catalyst to flow freely in pipe I2 afluidizing gas is injected therein through pipes 2|. By the same tokento .fluidize the catalyst in pipe I8, gas is injected through pipes 20causing the density in pipe I8 to be less than that in pipe I2. Hence.catalyst will ilow by the means indicated, i. e., diierence in densitiesbetween the material in pipes I2 and I8, in the indicated direction. Itis to be understood that the amount of gas injected into pipe I2 is muchless than that injected into pipe I8, say one-fourth as much or less.

There is also discharged into the reactor a quantity of butylene, thismaterial being supplied through line 5. The catalyst and the butyleneare mixed in mixing device 24, and the mixture is then caused to owupwardly in the reactor. The temperature of the gas in line 5 enteringthe reactor is about 1000 F., while the catalyst in line I8 is at atemperature of about l250 F. The gas and catalyst are mixed inproportions such that the temperature of the mixture is about 1150 F.with most catalysts and we prefer to maintain a density of thesuspension in the region just above the mixing device 24 of from about8-25 lbs/cu. it. which condition is attained by regulating the gasvelocities between 1 and 10 ft. per second where the particle catalystsize is from 200-400 mesh. Also a gas pressure of about mm. of mercuryis preferred within the reactor for the reaction. Under the conditionsstated, the reaction occurs to form ordinarily, butadiene fromnormal-butylene, and then by means which will be subsequently explainedmore fully hereinafter, the bulk of catalyst. is separated from thereaction mass and gravitates from the bottom of the reactor from whichit is withdrawn through standpipe 25, mixed with air in a mixing device28, the air entering through line 30, and thence conveyed through pipe3| into a regenerator 3,5. The dimensions of regenerator 35 and the gasvelocities are such dimensions that when the catalyst is mixed with therequired amount of air or other free oxygen containing gas, the densityof the mixture is from about 8 to 25 lbs/cu; ft. The catalyst in line 25is'at a temperature of 1050 F.1,150 F., and under these conditions whenmixed with air at ordinary atmospheric temperature in mixer 28 activecombustion takes place in regenerator 35 with the consumption ofcarbonaceous deposits produced on the catalyst as a result of thereaction taking place in reactor I. Ordinarily it is preferable tooperate regenerator 35 under superatmospheric pressure, say pressures upto 1-5 lbs/sq. in,

gauge or higher, as dictated by economic considerations, ln order toaccelerate the oxidation of the contaminating carbonaceous material. Theue gas and the regenerated catalyst are withdrawn from regeneratorthrough line 40 and discharged into a cyclone separator 4| built intothe top of hopper I0. The separator effects separation of theregenerated catalyst from the flue gas, and the latter is withdrawnthrough line 42 and, if desired, sent' to a second cyclone separater toremove further quantities of catalyst. In some cases, it is desirable toemploy three cyclones or even more to insure complete removal andrecovery of catalyst from iiue gas. The hot iiue gases substantiallyfreed of catalyst may then be passed through a waste heat boiler torecover a portion of their energy content. The catalyst separated incyclone separator 4| gravitates into hopper l and is recycled to thereactor in the manner previously described.

In the drawings, we have shown means for controlling the regenerationtemperature of the catalyst in regenerator 35. As shown, catalyst, thatis regenerated catalyst, may be withdrawn through hopper I0 through line62, mixed with air from line 60 in injector 6I, thence dischargedthrough cooler 63 and line 50 into regeneration vessel 35. The cooledregenerated catalyst may be at a temperature of say 30D-500 F. as itenters the regenerator, and may be in the proportions of say lo-2 ormore parts by weight of regenerated catalyst per part of unregeneratedcatalyst. 'Ihe cooler regenerated catalyst serves to increase the heatcapacity of the mixture and temper the exothermic reaction by absorbingheat released during regeneration.

Referring again to reactor l, it will be noted that a second chamber 10is superimposed at the top of reactor. This chamber contains thereaction products and catalyst added to quench the reaction mixture. Themanner of adding the catalyst will be presently described, but first letit be observed that the newly added catalyst plus the remainder of theoriginal catalyst not separated, together with the reaction mass, areWithdrawn overhead through line 12 and passed into a cyclone separator15 where the bulk of the quenching catalyst and the catalyst notpreviously removed are separated from the vapors. The separated catalystpasses into a receiving hopper 10 and in this hopper is at a temperatureof about 950 F. One'streain' of catalyst is withdrawn from hopper 18through line 80, communicating in its lower end with standpipe 25, asshown. The other stream of catalyst is withdrawn through line 82carrying a flow control valve 83 at its lower end and thence dischargedinto bend 84 Where it is mixed with a gas such as methane dischargedinto 84 through pipe 85, and thereafter the catalyst is passed upwardlythrough line 90 through a heat exchanger 95 where the catalyst is cooledto a temperature such that when withdrawn through line |00 it is at atemperature of about 600 F., whereupon it is inJected into the reactionmass in reactor I after removal from the reaction mass of the bulk ofthe catalyst with which it was previously associated, and thereafter thequenching catalyst carried upwardly in suspension into quenching chamber10 previously mentioned. The amount of catalyst recycled from hopper 18to quenching chamber 10 will depend of course entirely on the amount ofgas and catalyst iiowing into chamber 10 and the temperature thereof. Wehave found that good results are obtained by recycling to zone 10 fromhopper 18 suiiicient rality of cyclone separators 28.

catalyst so that a temperature of S50-1050 F. prevails in chamber 10. Inany event, it is usually preferable to add suiiicient catalyst to lowerthe temperature of the reaction mass to about 1000 F. or lower becauseat this temperature undesired side reactions are prevented and thedecomposition of the desired butadiene is substantially prevented. Inother words, the selectivity is improved by quenching in the mannerdescribed, which means that the per cent of the material desired ishigh. The gases freed from catalyst in separator 15 are withdrawnthrough line 20 and these are preferably passed through a heat exchanger|22 where they are cooled to about 600 F., thence withdrawn through line|25 and passed into Cottrell precipitator |30 where a catalyst isseparated and recycled to line 25 through line |32. The gases are drawnoverhead from separator |30 through line |35 and pass through a Cottrellprecipitator |40 where more catalyst is separated out and the separatedcatalyst is withdrawn through line |44 and recycled through 1ine3l toregenerator 35. The reaction products now containing only minor amountsof catalyst are withdrawn from Cottrell precipitator through line |50,thence further cooled in cooler |55, thence discharged through line |58into an oil Washer |60 where the last traces of catalyst are removed,the scrubbing oil being discharged into the washer through line |62. Thewashed gases are withdrawn through line |65, passed through entrainmentseparator |10 and thence to a pump in which they are compressed landcondensed prior to separation in a suitable system. The pressureconditions, i. e., the partial vacuum previously referred to in reactoris maintained through pump and suitable valves, in known manner.

Referring now to Fig. II for a detailed description of our improvedreactor and its immediate accessory apparatus, it will be observed thatthe catalyst and the butylene enter the reaction vessel I and pass intothe mixing chamber 24 and thence are delivered into the reaction chamber25 where the main reaction takes place, the catalyst being in the formof a dense mass or phase thoroughly intermixed with the reactant.Disposed about the reaction chamber 25 are a plu- These separators arearranged contiguously in the form of a ring or circle about the reactionvessel, and in escaping from reaction vessel 25 the uidized mass andreactant gas are forced into the separators 20. The bulk of thecatalyst, usually over A%, is separated from the gases and gravitates tothe bottom portion 36 of the reaction vessel, while the gases flowupwardly through outlet pipes 29, thence through pipe 32 into quenchingchamber 10. The catalyst which is separated in the separators 21collects in the bottom of the reaction vessel, as indicated by thecatalyst level line L, and is withdrawn from the said reactor andarranged such as to maintain the heated catalyst continuously in thesaid reaction vessel.

As is known by those familiar with this particular art, the types ofcata-lyst which may be employed for dehydrogenations are many andvaried. One of these catalysts is metallic nickel. Heretofore thediiiiculty withmetallic nickel has been that it is so reactive that itis not usable because it not only accelerates the formation of, say,butadiene from `butylene but attacks the butadiene to decompose it. Inthe type of operation which we have described herein, a very activecatalyst such as nickel may be successfully employed because thecombination of controlled contact time, finely divided catalyst andquenching features enables us to discontinue the reaction and to limitit to a very short period of time of contact between reactants and thenickel at reaction temperatures. In the case of other catalysts such assilica-alumina compositions, alumina-tungsten, alumina-chromium,alumina-molybdenum, the various metallic oxides, and the like, such ascopper oxide, nickel oxide, cobalt oxide or mixtures of the same wherethe catalyst is less active, our process is also of value not only fromthe standpoint of quenching the reaction but also from the standpoint ofsupplying at least a portion of the heat necessary for the reaction byrecycling hot regenerated catalyst to the reaction zone. Instead ofusing one of the foregoing catalysts, we may use a catalyst which isvery effective for the dehydrogenation of butylene to butadiene, namely,a catalyst consisting of a major portion of magnesium oxide, a minorportion of iron oxide, a promoter such as KzO, and a stabilizer such asCuO. This catalyst was disclosed in the application of Kenneth K.Kearby, Serial No. 430,873, led February 14, 1942, and a preferredmodification of that catalyst has the following composition in parts byweight; about '78.5 parts MgO, about 20 parts FeaOa, about 5 parts ofCuO and about 1.5 parts KzO. This composition may be modified asdisclosed in said application. The value of that catalyst is that itisinsensitive to steam or not adversely affected by steam and,consequently, our present process could be operated to dehydrogenatebutylene to butadiene employing the last-named catalyst in the presenceof added superheated steam, which steam might supply a substantialquantity of the heat necessary to carry out the reaction. In otherwords, the butylene entering line of Fig. I might be heated to atemperature of say 900 F. and thence discharged into reactor I where itcontacts'steam superheated to a temperature of say 1400 F. or higher,and mixed in such proportions with the hot catalyst, the butylene, andthe steam as to provide a reaction mixture having a temperature ofaround 1100 F. Steam, of course, could be introduced through lines 20,thence through line I8 into reactor I, or steam could be injecteddirectly into reactor I. The catalyst just mentioned is regeneratedby'contact with steam at 1400 F. or thereabouts where according to thewater-gas reaction, the carbonaceous contaminants on the catalyst formwith said steam, CO and CO2.

To recapitulate, our present invention involves the concept ofcontrolling accurately the contact time between a gaseous reactant and asolid catalyst, and while we in detail in connection with the specicproblem of dehydrogena'ting an olefin, obviously the inventive conceptis applicable to a great number of processes, such as gas oil cracking,desulfurization, aromatization, oxidations, simple and destructivehydrogenations, chlorinations, and numerous other gas phase reactionswhere contact time is an important consideration from the standpoint ofyields or for other reasons. It will be noted that according to ourprocess, we prefer to quench the reaction ass by means of a cooledsolid, such as a solid c talyst added in sumcient quantity to lower thereaction mass to temperahave described the invention tures substantiallybelow reaction temperatures, and since the process may be operated toquench the catalyst just above the reaction zone, very short contacttimes may be effected. On the other hand, if longer contact time betweenreactant and catalyst is desired, the quenching may be performed in asubsequent stage, say by adding cooled catalyst in line 12. It will beunderstood that instead of using catalyst to quench the reaction mass,we may use an inert solid such as sand, lime, or refractory materialwhich is added in suicient quantity and at a sufficiently lowertemperature to effect the desired result.

Other features of our invention involve, as heretofore set forth, anup-flow standpipe arrangement for adjusting pressure differentialsbetween the reaction zone and the regeneration zone; another featureinvolves furnishing at least a portion of the heat required forendothermic reactions by supplying the proper amount of heated catalyst.Finally, the catalyst flowing in the various means may be uidized bysteam in the case Where the catalyst is not affected by steam asheretofore mentioned, or by the introduction of other gases such asmethane, CO2, CO, nitrogen, and the like; that is to say, these gasesmay be added through lines 60 and 20 and at other points in the systemheretofore mentioned, to attain the desired fluidity of catalyst.

The pressure in reactor I may vary from about mm. of mercury to aboveatmospheric pressure, subatmospheric pressure being preferred. Thetemperature conditions prevailing within the reactor I may vary fromabout 900 F. to 1400 F. depending on the contact time between thereactants an. catalyst in dehydrogenation, and in the case of butylenedehydrogenation the contact times may vary from a fraction of a secondup to 5 seconds, with temperatures of the order of 1300 F. to 1400" F.preferred and contact times of less than and up to 5 seconds.

Many modifications of our invention will be obvious to those skilled inthis particular art.

What we claim is:

1. A continuous method for dehydrogenating butylene to butadiene whichcomprises discharging the preheated butylene into a reaction zone,simultaneously discharging into said reaction zone a dehydrogenationcatalyst in the form of a udized powder, causing the butylene and theuidized powdered catalyst to remain in contact with each other attemperatures within the range of from 9501400 F. for a period of notless than 1 second and not more than 5 seconds by. adding a quantity ofcooled catalyst to the reaction mass when they have been in contact witheach other for the time period stated, withdrawing the reaction massfrom the reaction zone, separating the catalyst from the reaction mass,recovering butadiene therefrom, regenerating the catalyst and returningthe regenerated catalyst substantially uncooled to the reaction zone;

2. The method set forth in claim 1 wherein a portion of the catalystseparated from the reaction mass is cooled and recycled to the reactionmass where-it serves to quench said reaction mass.

BRUN() E. ROETHELI. WALTER G. SCHARMANN.

